Objectives: The present study aimed to identify the prevalence of focal uptake in the colon on 18 fluorine-fluorodeoxyglucose ( 18 F-FDG) positron emission tomography/computed tomography (PET/CT) studies performed for the evaluation of malignancies other than colon, to detect the rate of malignancy in incidental focal 18 F-FDG avid colonic lesions and to investigate if any possible role of maximum standardized uptake value (SUV max ) values in the discrimination of malignant lesions from premalignant and benign ones exist. Methods: We retrospectively reviewed the files of 8,017 patients with known or suspected malignancy, who underwent whole-body 18 F-FDG PET/CT at our institution during the period November 2017 to November 2019. Patients showing a single site of focally increased colonic 18 F-FDG uptake that was more intense compared to liver uptake on 18 F-FDG PET studies and referred to colonoscopy were enrolled in the study. Results: Fifty two patients (83.8%) had at least 1 corresponding lesion on colonoscopy, whereas in 10 patients no lesion was detected. Subsequent histopathological examinations revealed no corresponding lesion in 13 (13.7%), a benign lesion in 18 (18.9%), hyperplastic polyp in 10 (10.5%), low-grade polyp in 16 (16.8%), high-grade polyp in 29 (30.5%) and malignant lesion in 9 (9.5%) of the focal 18 F-FDG uptake sites. According to histopathology results, statistically no significant difference was found between the SUV max measurements of malignant and benign cases (p>0.05) but the average SUV max measurements of malignant cases were found to be significantly higher than lower + high-grade cases (p<0.05) and hyperplastic polyp cases (p<0.01). Conclusion: In conclusion, any unexpected focal 18 F-FDG uptake in 18 F-FDG PET/CT studies is suspicious for malignancy and should be clarified by colonoscopy. The intensity of 18 F-FDG uptake does not preclude the application of colonoscopy and histopathological verification of the lesion if there is any.

Objectives: The aim of this study was to compare the treatment responses after ablation with 30-50 mCi radioactive iodine (RAI) and 100 mCi RAI in patients with differentiated thyroid cancer (DTC) who were in the low-risk group according to 2015 American Thyroid Associations Classification (ATA 2015) criteria. Methods: Between February 2016 and August 2018, 100 patients who received RAI treatment in our clinic after total thyroidectomy and who were in the low-risk group DTC were included in this retrospective study. These patients were divided into 2 groups: low-activity (30-50 mCi) (group 1) and high-activity (100 mCi) (group 2). While 54 patients were treated with low activity, 46 patients received high activity RAI. The 2 groups were compared according to the 1 st - and 3 rd -year treatment response status. Results: According to the first-year follow-up, 15 patients were accepted as indeterminate response and 85 patients as excellent response. Three (5.5%) of the patients who were accepted as indeterminate response were in group 1 and 12 (26%) were in group 2. According to the third year follow-up, 1 patient in group 1 and 3 patients in group 2 were accepted as indeterminate response. No biochemical incomplete response or recurrent disease was detected. In the chi-square analysis performed to investigate the relationship between the first-year treatment response and RAI activities, a significant relationship was found (p=0.004). In the Mann-Whitney U test performed to investigate the parameters that may be effective in the treatment response, only the preablative serum thyroglobulin value was shown to have a significant difference between the two groups (p=0.01). In the long-term follow-up of the patients, based on the third year treatment response data, chi-square analysis was performed to evaluate the two groups in terms of treatment responses, and no statistically significant relationship was found (p=0.73). Conclusion: Ablation with 30-50 mCi can be safely applied in DTC patients who are in the ATA 2015 low-risk group and are planned for RAI ablation treatment.

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Purpose To evaluate whether metabolic and volumetric data from 68Ga-PSMA PET/CT performed during staging of de-novo high-volume mCSPC patients who received docetaxel could be used to predict survival. Methods Forty-two de-novo high-volume mCSPC patients, who received ADT + Docetaxel and underwent 68Ga-PSMA PET/CT for staging, were included in the study. The association between patients’ pathological data, all PSA measurements, treatments they received, the data obtained from 68Ga-PSMA PET/CT and progression-free and overall survival were examined. Results In the multivariate analysis, PSMA-TV (primary) and PSMA-TV (WB) variables were shown to be independent negative predictors of overall survival. For the threshold value of 19.91 cm3 obtained for PSMA-TV (primary), HR was calculated as 6.31, the 95% confidence interval (CI): 1.01–39.18, P = 0.048. For the threshold value of 1226.5 cm3 obtained for PSMA-TV (WB) variable, HR was calculated as 58.62, the 95% CI: 2.55–1344.43, P = 0.011. In our study, SUVmax (WB) variable was found to be an independent and negative predictor of progression-free survival. For the determined threshold value of 17.74, HR was calculated as 16.24, 95% CI: 1.18–22.76, P = 0.037. Conclusion Metabolic and volumetric data obtained from 68Ga-PSMA PET/CT can be used to predict survival in de-novo high-volume mCSPC. Our results show that in ADT + Docetaxel receiving patients, a subgroup with higher PSMA-TV (WB) values have a significantly worse prognosis. This situation suggests that the high-volume disease definition in the literature may be insufficient for this group, and that 68Ga-PSMA PET/CT can play an essential role in demonstrating the heterogeneity within the group.